This proposal concerns a biochemical investigation of mechanisms involved in the transcription of specific genes during normal cell growth and differentiation and in malignant cells. The major emphasis is on specific 5S and tRNA (class III polymerase) and histone (class II polymerase) genes expressed in amphibian oocytes and embryos or in cultured human cells. Human and murine 5S and tRNA genes and human and amphibian histone gene clusters have been cloned in this lab and are being characterized with respect to structure and organization. Most all of the various genes have been shown to be accurately transcribed by purified class II or III RNA polymerases in the presence of crude cellular extracts or purified or partially purified factors derived from these extracts. In the future we will (1) continue the structural studies of the histone genes and determine which clusters are active in vivo and possible changes in the patterns of expression of the cloned variants; (2) continue the purification of the human and amphibian transcription factors which are necessary and sufficient for transcribing the purified genes; (3) determine the sites and mechanisms of action of these factors, including interactions with DNA sequences, with RNA polymerases, and with each other; (4) search for other factors which regulate or modulate the activity of these genes, including those which may operate through modifications of chromatin structure.